Machine operators experience significant levels of vibration, which may cause discomfort. Many regulatory bodies have imposed restrictions on the vibration levels that an operator can be exposed to over time. To comply with these restrictions, an operator's time on a particular machine can be limited. Specifically, the operator may be required to cease operation of the machine after experiencing a certain vibration level for a predetermined time. Alternatively, an active vibration management system may be employed in an attempt to reduce the average vibration level experienced by the operator and, thereby, prolong the allowed time on the machine.
Various feedback control systems have been proposed for actively reducing vibrations in a machine. Many of these systems involve sensing vibrations produced in the machine and generating canceling vibrations having a frequency component with essentially the same amplitude, but shifted by 180 degrees in phase. In order to be effective without magnifying the problem, these control systems must overcome a time lag between sensing the machine vibrations and generating the canceling vibrations.
U.S. Pat. No. 7,206,681 (“the '681 patent”), issued to Casey et al. on Apr. 17, 2007, describes an adaptive vibration management system that is configured to predict vibration levels produced by the machine. The predicted vibration levels are extrapolated based on current vibration levels and input commands indicative of anticipated operations of the machine. The system then adjusts an actual response of the machine (e.g., reducing a rate of acceleration) based on the predicted vibration levels to reduce the resulting vibration effects on the operator.
While the '681 patent may help reduce the vibrations transferred to the operator, the system may have several shortcomings. For example, the system of the '681 patent cannot differentiate between predictable engine vibrations and unpredictable external vibrations (e.g., vibrations caused by the impact of implements striking the ground). The external vibrations may not be repeated and can be several orders of magnitude greater than the amplitude of the engine vibrations. Therefore, sensing the totality of vibrations and responding to the external vibrations may lead to improper corrective measures that actually worsen the vibrations experienced by the operator.
The disclosed control system is directed to overcoming one or more of the problems set forth above and/or other problems in the prior art.